In a conventional toilet bowl, since solid pins are used for the hinges supporting the toilet seat and the toilet lid, the friction on the sliding contact portions between each solid pin and the pin insertion holes formed in the toilet seat and the toilet lid is likely to decrease. For that reason, the lid often unexpectedly closes due to its own weight causing an impact, when the lid, for instance, slips down out of the hand at the time of opening the lid. This impact closing of the lid may result in not only making an unpleasant noise but also damaging the toilet bowl. Such a tendency is greatly promoted as the sliding contact portions mentioned above wear, and such wearing is likely to occur, for the lid is generally opened or closed so often.
When a spring pin is used for a pivot, as mentioned in Japanese Patent 56-8607, the friction acting in the sliding contact poritions is automatically compensated for by the force of the pin which acts to expand the spring pin itself in the radial direciton, so that the lid is prevented from closing due to its own weight.
However, it has recently turned out that when a spring pin rotates excessively in the pin insertion hole or, when an abnormal axial force acts on the spring pin, the spring pin is forced to vibrate in the hole and slip forward in the axial direction of the spring pin and even unexpectedly drop out of the hole.